README.md

websockify: WebSockets support for any application/server

websockify was formerly named wsproxy and was part of the
noVNC project.

At the most basic level, websockify just translates WebSockets traffic
to normal socket traffic. Websockify accepts the WebSockets handshake,
parses it, and then begins forwarding traffic between the client and
the target in both directions.

WebSockets binary data

Websockify supports all versions of the WebSockets protocol (Hixie and
HyBI). The older Hixie versions of the protocol only support UTF-8
text payloads. In order to transport binary data over UTF-8 an
encoding must used to encapsulate the data within UTF-8. Websockify
uses base64 to encode all traffic to and from the client. This does
not affect the data between websockify and the server.

Websock Javascript library

The include/websock.js Javascript library library provides a Websock
object that is similar to the standard WebSocket object but Websock
enables communication with raw TCP sockets (i.e. the binary stream)
via websockify. This is accomplished by base64 encoding the data
stream between Websock and websockify.

Websock has built-in receive queue buffering; the message event
does not contain actual data but is simply a notification that
there is new data available. Several rQ* methods are available to
read binary data off of the receive queue.

See the "Wrap a Program" section below for an example of using Websock
and websockify as a browser telnet client (wstelnet.html).

Additional websockify features

These are not necessary for the basic operation.

Daemonizing: When the -D option is specified, websockify runs
in the background as a daemon process.

SSL (the wss:// WebSockets URI): This is detected automatically by
websockify by sniffing the first byte sent from the client and then
wrapping the socket if the data starts with '\x16' or '\x80'
(indicating SSL).

Session recording: This feature that allows recording of the traffic
sent and received from the client to a file using the --record
option.

Mini-webserver: websockify can detect and respond to normal web
requests on the same port as the WebSockets proxy and Flash security
policy. This functionality is activate with the --web DIR option
where DIR is the root of the web directory to serve.

Wrap a program: see the "Wrap a Program" section below.

Implementations of websockify

The primary implementation of websockify is in python. There are also
alternative implementations in the other/ subdirectory.

Here is the feature support matrix for the the websockify
implementations:

Wrap a Program

In addition to proxying from a source address to a target address
(which may be on a different system), websockify has the ability to
launch a program on the local system and proxy WebSockets traffic to
a normal TCP port owned/bound by the program.

The is accomplished with a small LD_PRELOAD library (rebind.so)
which intercepts bind() system calls by the program. The specified
port is moved to a new localhost/loopback free high port. websockify
then proxies WebSockets traffic directed to the original port to the
new (moved) port of the program.

The program wrap mode is invoked by replacing the target with --
followed by the program command line to wrap.

`./websockify 2023 -- PROGRAM ARGS`

The --wrap-mode option can be used to indicate what action to take
when the wrapped program exits or daemonizes.

Here is an example of using websockify to wrap the vncserver command
(which backgrounds itself) for use with
noVNC: